1. Field of the Invention
This invention relates to an electric motor drive device for a camera and more particularly to a motor drive device provided with driving mechanisms such as an electric motor winding, rewinding and counter mechanisms.
2. Description of the Prior Art
There have been known varied kinds of electric motor drive devices for cameras arranged to have film winding and rewinding operations carried out by means of drive motors. These known electric motor drive devices include a type wherein two one-way clutches each of which is capable of transmitting a rotation force in only one direction different from that of a rotation force to be transmitted by the other are mounted on the output shaft of the motor. The driving force of the motor is transmitted to a film winding mechanism, for example, when the motor rotates in a normal direction and to a film rewinding mechanism when it rotates in the reverse direction. This type of device is known, for example, from U.S. Pat. No. 3,981,022.
The electric motor drive device of the above stated type having one-way clutches obviates the necessity of engaging and disengaging gears for change-over between a film winding operation and a film rewinding operation. Therefore, the change-over can be smoothly accomplished. Besides, tooth faces of gears wear out to a lesser degree. On the other hand, however, the construction of the device is complex. Further, it is another shortcoming of the device of the prior art that A film counter, an automatic exposure control device, and the like must be arranged such that they will be reliably charged with each winding of one frame portion of the film. It is desirable that the charged phase preferably coincides with the charged phase of a shutter charge mechanism or the like disposed on the side of the camera. In the case of the electric motor drive device using one-way clutches, however, the one-way clutches are interposed between a driving gear and a film winding transmission member engaging the film winding shaft of the camera. Therefore, play or the like in the one-way clutches causes a phase discrepancy between the winding transmission member and the driving gear. It has been difficult, therefore, to attain coincidence in phase between the charging action performed within the camera and the charging action performed within the electric motor drive device or unit. It has been a further shortcoming of the electric motor drive device of this type that a film counter, etc. cannot be accurately operated because of the above stated phase discrepancy.